Ch.18.1 Astronomy: The Original Science! P.554 Take out flashcards. Please open your books and Label your IAN with today’s title. Cut out and glue in your tub notes.

Objective: Describe the guys with their eyes on the skies!! History of Astronomy Objective: Describe the guys with their eyes on the skies!!

People in ancient cultures used the seasonal cycles of the stars, planets, and the moon to mark the passage of time. For example, by observing these yearly cycles, early farmers learned the best times of year to plant and harvest various crops. Over time, the study of the night sky became the science of astronomy. Astronomy is the study of the universe. Although ancient cultures did not fully understand how the planets, moons, and stars move in relation to each other, their observations led to the first calendars. Mayans

Greeks: Aristotle

Ancient Observations The ancient Greeks observed the sky and noticed that the moon, sun, and stars seemed to move in a circle around the Earth. It seemed that the Earth was not moving and everything in the heavens revolved around the Earth. As it turned out, it was very difficult to prove that the planets did not revolve around the Earth without leaving the planet.

Aristotle: Earth is a Sphere! Aristotle knew that the earth was a sphere. -each part of the earth is trying to be pulled to the center of the earth, and so the earth would naturally take on a spherical shape. the shadow of the earth on the moon during a lunar eclipse was always circular. The only shape that always casts a circular shadow is a sphere. as one traveled more north or south, the positions of the stars in the sky change. There are constellations visible in the north that one cannot see in the south and vice versa.

Geocentric Theory Ancient Greeks such as Aristotle believed that the universe was perfect and finite, with the Earth at the exact center. This is the geocentric theory, which has the planets, moon, sun, and stars revolve around the Earth.

Claudius Ptolemy 140 AD further developed the geocentric model (Earth-centered) planets move on small circles that move on bigger circles – explained why Mars moved backward accepted for 1,500 years M E

What happened next?

Nicolaus Copernicus Early 1500's developed heliocentric model (sun-centered) Used geometry to determine Earth to Sun distance and the planets arrangement/movement Still thought orbits were perfect circles

Humor What did Copernicus say about Ptolemy’s theory of an Earth-Centered Universe? Ptolemy another one! Theories of Space Science are continually changing!

Tycho Brahe late 1500's believed much of what Copernicus observed, except that planets travel on orbits that are perfect circles his team observed and recorded the positions of the planets for more than 20 years

Earth

Brahe used a mural quadrant, which is a large quarter-circle on a wall, to measure the positions of stars and planets.

Fun Fact Brahe was known to be eccentric! As a young man, he insulted a fellow student and was challenged to a duel. During the duel, part of his nose was chopped off and he wore a nose prosthesis for the rest of his life. Talk about dueling theories of space science!

Johannes Kepler 1600's One of Brahe’s assistants proved that orbits were NOT perfect circles: they are ellipses sun

Galileo Galilei Early 1600's Changed lenses in telescope to mirrors Using the telescope he proved the heliocentric model with the following discoveries: 4 moons orbiting Jupiter phases of Venus craters on the Moon Galileo

Heliocentric Theory Prevails Since Galileo’s theory clashed with the religious views of the time, he underwent many trials and tribulations, eventually being sentenced to house arrest for his remaining years. But his view has withstood the test of time. Today we talk about our solar system, not our Earth system

Theory Has a very different meaning in science than in everyday life. “The detective has a theory about who robbed the bank.” This is a guess. When scientists use the word theory it is not used as a guess.

Theory defined An explanation based on many observations during repeated experiments that is valid only if it is consistent with observations, makes predictions that can be tested, and is the simplest explanation. A logical, time tested explanation for events that occur in nature.

So the theory of gravity, theory of electricity, the germ theory of disease, and the theory of evolution are tested, accepted explanations for events that occur in nature. Theories can really never be completely proven, only disproved. When new evidence comes along, we must modify our theory or at times even get rid of it and start over again.

Theories in Science can change! Ptolemy’s earth centered theory of the solar system is an example of what can happen when new evidence comes along. When Copernicus showed that putting the Sun in the center made it much easier to predict the planets motions, the old earth centered theory was discarded and a new one developed.

Who’s left? Make another box for our last scientist: Sir Isaac Newton!

Sir Isaac Newton 1665 explained why the planets stay moving around the sun: inertia and gravity 1st law: inertia -a body will continue in a straight line unless acted on by a force. Gravity keeps the moving planets in orbit around Sun

Newton Brainpop

Modern Astronomy The invention of the telescope and the description of gravity were two milestones in the development of modern astronomy. In the 200 years following Newton’s discoveries, scientists made many discoveries about our solar system. But they did not learn that our galaxy has cosmic neighbors until the 1920s.

Edwin Hubble: Beyond the Edge of the Milky Way Before the 1920s, many astronomers thought that our galaxy, the Milky Way, included every object in space. In 1924, Edwin Hubble proved that other galaxies existed beyond the edge of the Milky Way. His data confirmed the beliefs of some astronomers that the universe is much larger than our galaxy. Today, larger and better telescopes on the Earth and in space, new models of the universe, and spacecraft help astronomers study space. Computers help process data and control the movement of telescopes. These tools have helped answer many questions about the universe. Yet new technology has presented questions that were unthinkable even 10 years ago

Greatest Discoveries w/ Bill Nye: Astronomy